Refractive index is a physical property that is greatly affected by constituent elements, molecular structure, crystal structure and electric charge, and is therefore not easily adjusted. Normally, the refractive index of polymers is limited to the vicinity of 1.4 to 1.6, demonstrating a narrower range of variation in comparison with the range of 0.17 (silver) to 4.2 (silicon) of inorganic materials. This is due to the main component of polymers being mainly composed of carbon that has low atomic refraction. However, in order to take advantage of the moldability and light weight of polymers, refractive index has been increased through molecular design such as the introduction of sulfur atoms or bromine atoms in applications such as lenses. In addition, although metal oxide fine particles having a high refractive index (such as alumina (see, for example, Patent Document 1), titania or zirconia) have been compounded since modulating the refractive index of high-performance polymers cannot be achieved by rearranging constituent elements, in order to enhance transparency, it is necessary to uniformly disperse metal oxide fine particles having a size on the order of several nanometers, thereby making the procedure difficult.
Although research and development has been actively conducted on organic EL, LED lighting or laser elements, since these devices require that the generated light be efficiently extracted or confined, the refractive index of the optical materials used therein is an important factor. The aforementioned optical devices require microprocessing into thin layers and complex shapes, and polymers such as photoresists are suitable as polymers applied to such optical devices.
Patent Document 1: Japanese Patent Application Laid-open No. H9-221598